Abstract: A method of repairing a thermal barrier coating on a component designed for use in a hostile thermal environment, such as turbine, combustor and augmentor components of a gas turbine engine. The method is particularly suited for completely removing a thermal insulating ceramic layer of thermal barrier coating system that includes a metallic bond coat, such as a diffusion aluminide or MCrAlY coating, between the surface of the component and the ceramic layer, while leaving the bond coat substantially undamaged. Furthermore, the method of this invention includes a technique by which ceramic material within cooling holes in the component can be removed without damaging the underlying bond coat. The process steps generally include removing the ceramic layer from the surface of the component by subjecting the ceramic layer to a caustic solution at an elevated temperature and pressure, and then removing ceramic material from the cooling hole by carefully directing a high-velocity fluid stream into the cooling hole.

Abstract: A thermal barrier coating (TBC) system and method for forming the TBC system on a component designed for use in a hostile thermal environment, such as superalloy turbine, combustor and augmentor components of a gas turbine engine. The TBC system exhibits improved spallation resistance as a result of having a bond coat formed to contain a dispersion of oxide particles in its outer surface region. A method for preferentially entrapping oxide particles in a bond coat entails depositing the oxide particles on the surface of the component prior to forming the bond coat, which may be a diffusion aluminide or an aluminized overlay coating. Deposition of the bond coat causes the oxide particles to become dispersed in the outer surface region of the bond coat. A particular feature of this invention is the ability to preferentially entrap oxides of elements that are not present in the bond coat or a substrate region of the component on which the bond coat is formed.

Abstract: A thermal barrier coating system and a method for forming the coating system on a component designed for use in a hostile thermal environment, such as superalloy turbine, combustor and augmentor components of a gas turbine engine. The method is particularly directed to a thermal barrier coating system that includes a thermal insulating ceramic layer and a diffusion aluminide bond coat on which an aluminum oxide scale is grown to protect the underlying surface of the component and to chemically bond the ceramic layer. The bond coat is formed to contain an additive metal of platinum, palladium, rhodium, chromium and/or silicon, and an additive element of yttrium and/or zirconium, with possible additions of hafnium. The bond coat may be formed by codepositing aluminum with the active element, or by depositing the additive metal and active element on the surface of the component, and then aluminizing to form the diffusion aluminide bond coat.

Abstract: A method is provided for enhancing to a selected coating range a substantially unused protective coating, including aluminum, on an article surface, for example an airfoil surface of a gas turbine engine turbine blade. The protective coating is enhanced without removing such unused coating. The unused coating is evaluated to identify at least one coating region that deviates from the selected coating range by being deficient in at least one of chemistry and physical condition, for example thickness. At least the coating region is enhanced to the selected coating range by applying over the identified coating region at least one secondary element selected from Pt, Rh, Pd, Cr, Si, Hf, Zr, and Y. At least the coating region is heated to diffuse the secondary element into the protective coating to provide a treated coating region. Then at least the treated coating region is aluminided.

Abstract: A coated article is provided with a coating stabilizing portion in a coating combination on a substrate of the article. The coating combination includes a coating diffusion portion on the substrate and an outer coating portion outwardly from the coating diffusion portion. The coating stabilizing portion is provided between the coating diffusion portion and the outer coating portion to inhibit diffusion of undesirable elements to an interface with the outer coating portion and to enhance mechanical properties.

Abstract: A process for forming a diffusion aluminide coating on a substrate, such as a component for a gas turbine engine. The process generally entails placing the substrate in a suitable coating chamber, flowing an inert or reducing gas into and through the coating chamber, and then aluminizing the substrate using an aluminizing technique with a substantially constant aluminum activity, such as a vapor phase deposition process. During the aluminizing process, the amount of unreacted aluminum within the coating chamber is controlled by altering the flow rate of the gas through the coating chamber so that a portion of the unreacted aluminum is swept from the coating chamber by the gas. The amount of unreacted aluminum swept from the coating chamber is regulated by metering the gas flow rate in order to control the aluminizing rate and aluminum content of the resulting aluminide coating.

Abstract: A method for removing products of hot corrosion and oxidation from selective portions of surfaces of a gas turbine engine, such as coatings and substrates, following exposure of the surfaces to hot oxidative gases of the turbine exhaust. The method involves a high temperature chemical reaction and has no detrimental effect on adjacent coatings and substrates that have not been attacked by the hot exhaust gases.

Abstract: A gas turbine engine hot section component having a ceramic thermal barrier coating is repaired by removing the ceramic thermal barrier coating, removing oxidation products and corrosion products from the metallic bond coating beneath the ceramic thermal barrier coating, applying a noble metal to the component, diffusing the noble metal into the component substrate, and aluminiding the component to provide an outermost noble metal-Al layer.

Abstract: A gas turbine engine hot section component having a ceramic thermal barrier coating is repaired by removing the ceramic thermal barrier coating, removing oxidation products and corrosion products from the metallic bond coating beneath the ceramic thermal barrier coating, applying a noble metal to the component, diffusing the noble metal into the component substrate, and aluminiding the component to provide an outermost noble metal-Al layer.

Abstract: A method for restoring a protective coating including a metallic environmental resistant coating of a coating total thickness within a coating design thickness range on a metal substrate of an article includes the application of a replacement material to at least one discrete local surface area on which an undesirable amount of degradation has occurred. Such degradation can extend through the protective coating into the metal substrate. The degradation product can include at least one of oxidation, coating rumpling, and coating voiding, for example, rumpling or voiding of a bond coat under a ceramic thermal barrier coating (TBC). The degradation product first is conditioned at the discrete local area to expose an underlying portion while retaining at least a portion of the metallic environmental coating on surface areas adjacent the discrete surface area. Then a replacement metallic environmental resistant material is applied, retaining the coating total thickness within the coating design thickness range.

Abstract: A method for preventing the deposition of material in an opening near a surface of an article, and a masking insert therefore. The method and insert are particularly suited for preventing the plating of a metal, such as platinum, on turbine airfoils or turbine blades and vanes having a complex geometry, as is the case when cast trailing edge cooling slots are present in the airfoil surface. The method entails the use of the masking insert, which is precisely configured to mask the cooling slots during plating by preventing circulation of the plating bath through the slots. For this purpose, the insert is equipped with appendages that are sized, shaped, spaced and oriented on a base member to register with, and preferably be received within, the cooling slots of an airfoil having a particular cooling slot design.

Abstract: A curved component such as a turbine airfoil, shroud, or combustor centerbody is prepared with a platinum or a platinum-aluminide protective coating over only a portion of the surface thereof. The coating may serve as an environmental coating, or as a bond coat of a thermal barrier coating system. The partial coverage is achieved by depositing platinum only over a portion of the surface of the component, typically including the concave portion in the case of an airfoil, optionally depositing an aluminum layer, and optionally interdiffusing the platinum and aluminum layers.

Abstract: A gas turbine engine hot section component having a ceramic thermal barrier coating is repaired by removing the ceramic thermal barrier coating, removing oxidation products and corrosion products from the metallic bond coating beneath the ceramic thermal barrier coating, applying a noble metal to the component, diffusing the noble metal into the component substrate, and aluminiding the component to provide an outermost noble metal-Al layer.

Abstract: A method for restoring or enhancing an environmental resistant coating of a coating total thickness within a coating design thickness range on a metal substrate of an article includes the application of a restoring or enhancing metal to at least one discrete local surface area. Then at least the discrete local surface area is coated with an environmental resistant coating. For use of the method to restore a coating on an article which has experienced service operation and the discrete surface area includes an undesirable amount of oxidation/corrosion products, the oxidation/corrosion products first are removed from an outer portion of the coating while retaining a coating present at the discrete surface areas and retaining the entire coating on surface areas adjacent the discrete surface areas. Then the restoration metal is applied.

Abstract: A method for preventing the aluminizing of cooling holes and internal surfaces of an airfoil during vapor phase aluminizing. The method generally entails flowing a gas through internal cavities of the airfoil and out through the cooling holes, while the surfaces of the airfoil are aluminized by vapor phase deposition. As a result of the outward gas flow, volatile activators and aluminum compounds are prevented from flowing into the cooling holes and internal cavity, thereby preventing aluminizing of the cooling hole walls and internal surfaces of the airfoil and interactions with any oxide deposits on the surfaces of the cooling holes and internal cavities.

Abstract: A component for use in a high-temperature environment such as the coating chamber of a PVD apparatus. A reflective coating on the component serves as a barrier to radiant heat transfer to the component by reflecting thermal radiation. The coating comprises at least one pair of reflective layers, each layer being formed of a material that is essentially transparent to electromagnetic wavelengths of between 500 and 3000 nanometers (nm). In addition, the material of the outermost layer of the pair has a higher index of refraction than the material of the other layer of the pair.

Abstract: A method of removing hot corrosion products from the surface of a component exposed to corrosive conditions at elevated temperatures, as is the case with turbine, combustor or augmentor components of gas turbine engines. The method is particularly suited for the removal of hot corrosion products from components protected with a diffusion aluminide coating, either as an environmental coating or as a bond coat for a thermal barrier coating (TBC). The processing steps of the method include immersing the component in a heated liquid solution containing acetic acid, and then agitating the surfaces of the component while the component remains immersed in the solution. In this manner, hot corrosion products on the surfaces of the component are removed without damaging or removing the diffusion aluminide coating. As a result, regions of the component from which the hot corrosion products were removed can then be repaired by a suitable aluminizing process.

Abstract: A method of forming a thermal barrier coating system on an article subjected to a hostile thermal environment, such as the hot gas path components of a gas turbine engine. The coating system is generally composed of a ceramic layer and preferably a bond coat that adheres the ceramic layer to the component surface. Surface features such as grooves are cast directly into the surface of the component. If the bond coat is present, the grooves in the component surface cause the bond coat to also have grooves that generally correspond to the grooves in the component surface.

Abstract: A heating apparatus and method for welding a superalloy article. In a preferred embodiment, the apparatus and method entail welding a superalloy article within an enclosure equipped with a thermal radiation-generating device that preheats the article to a temperature of at least 1500.degree. F. prior to welding. The invention more particularly provides a thermally-reflective coating on a reflector member positioned adjacent the thermal radiation-generating device for the purpose of reflecting thermal radiation emitted by the device into the enclosure. The device is then operated to heat the superalloy article to a suitable temperature, e.g., 1500.degree. F. or more, after which a welding operation is performed on the superalloy article.

Abstract: A thermal barrier coating (TBC) system, comprising a metallic bond coat on an article surface and an outer ceramic TBC is repaired by renewing without removing the bond coat. The outer ceramic TBC is removed to expose a bond coat substrate. At least one discrete local surface area of the article surface subject to bond coat degradation is selected from a thermal pattern unique to the article surface from service operation. At least one renewal metal selected from Pt, Rh, and Pd is applied at least to the selected discrete local surface area and heated to diffuse the renewal metal into the bond coat substrate. An environmental resistant coating selected from aluminides and alloys including aluminum is applied at least to the discrete local surface area over the renewal metal. Thereafter, an outer ceramic TBC is applied to the article surface.